| Controls | COPD | CV# % | ||||
| Nonsmoking | Smoking | GOLD 2 | GOLD 3 | GOLD 4 | ||
| Subjects n | 46 | 183 | 179 | 186 | 60 | |
| Rrs5 kPa·L−1·s−1 | 0.28 (0.47) | 0.29 (0.48) | 0.42 (0.67) | 0.46 (0.73) | 0.49 (0.72) | 5.3 |
| Insp | 0.27 (0.47) | 0.27 (0.43) | 0.37 (0.57) | 0.42 (0.63) | 0.45 (0.60) | 5.8 |
| Exp | 0.30 (0.53) | 0.31 (0.52) | 0.44 (0.70) | 0.47 (0.75) | 0.47 (0.78) | 6.4 |
| Xrs5 kPa·L−1·s−1 median (fifth percentile) | −0.07 (−0.16) | −0.08 (−0.18) | −0.15 (−0.42) | −0.26 (−0.54) | −0.40 (−0.66) | |
| Insp | −0.08 (−0.14) | −0.08 (−0.15) | −0.14 (−0.23) | −0.18 (−0.33) | −0.24 (−0.46) | |
| Exp | −0.07 (−0.18) | −0.07 (−0.22) | −0.17 (−0.54) | −0.31 (−0.70) | −0.51 (−0.88) | |
| ΔXrs kPa·L−1·s−1 | −0.01 (0.04) | −0.01 (0.07) | 0.04 (0.37) | 0.11 (0.51) | 0.26 (0.66) | |
| fres Hz | 12.0 (16.0) | 11.5 (16.4) | 17.2 (24.8) | 20.0 (27.5) | 23.6 (31.2) | 4.0 |
| Insp | 10.9 (15.1) | 10.3 (15.5) | 16.5 (22.4) | 18.8 (25.7) | 21.5 (29.8) | 4.1 |
| Exp | 12.3 (17.9) | 12.3 (17.8) | 17.7 (26.5) | 20.4 (28.4) | 24.4 (31.2) | 5.1 |
Data are presented as median (95th percentile) unless otherwise stated. n=654. COPD: chronic obstructive pulmonary disease; GOLD: Global Initiative for Chronic Obstructive Lung Disease; CV: coefficient of variation; Rrs5: resistance at 5 Hz; Insp: inspiratory; Exp: expiratory; Rrs5: reactance at 5 Hz; ΔXrs: difference between Insp and Exp values of Rrs5; fres: resonant frequency. #: mean over three measurements.